Validation of the 2019 EULAR/ACR classification criteria and clinical characteristics of childhood-onset Japanese patients with systemic lupus erythematosus

Objectives This study was aimed to evaluate the diagnostic performance of the 2019 European League Against Rheumatism/American College of Rheumatology (EULAR/ACR-2019) classification criteria of systemic lupus erythematosus (SLE) and to clarify the clinical characteristics of Japanese childhood-onset SLE (cSLE). Methods We retrospectively analyzed clinical data registered in the Pediatric Rheumatology International Collaboration Unit Registry (PRICURE) version 2 up to March 31, 2023. Frequencies of individual items within the EULAR/ACR-2019 criteria were compared with those observed in a Japanese adult SLE cohort. Results A total of 105 patients with cSLE, 19 with Juvenile dermatomyositis (JDM), 27 with primary Sjögren’s disease (pSjD), and 9 with mixed connective-tissue disease (MCTD) were included. The sensitivity of the EULAR/ACR-2019 criteria was 97.1%. The specificity was 94.7% for JDM, 92.6% for pSjD, 55.6% for MCTD, and 87.3% for all disease controls. cSLE patients in this cohort more frequently exhibited renal involvement, low serum C3 or C4 levels, and positivity for antiphospholipid and anti-double-stranded DNA antibodies, whereas joint symptoms were less common than in adult SLE patients. Conclusions Although the EULAR/ACR-2019 criteria are generally applicable, the limited specificity for MCTD necessitates careful differential diagnosis. Japanese cSLE is commonly characterized by renal involvement, hypocomplementemia, and SLE-related autoantibody positivity.